Since pawns can provide up to 4 guaranteed moves in each file, to say nothing of all the other pieces that can legally move to that file, this is pretty much a referendum on the longest English word that doesn't use any of the letters I-Z. According to the CSW word list used for international English-language Scrabble tournaments, that word is DEADHEADED, which would be represented as 1. d3 e6 2. a3 d6 3. h3 e5 4. a4 d5 5. e3 d4 (0-1)